偶然间发现，未指定代理时，urllib2使用了IE的代理设置。

以前未注意到该特性，是因为一直没给IE配置过代理。最近在使用IPRental的代理服务，它会自动给IE配置代理。

urllib2文档中有如下说明：

class urllib2.ProxyHandler([proxies])

Cause requests to go through a proxy. If proxies is given, it must be a dictionary mapping protocol names to URLs of proxies. The default is to read the list of proxies from the environment variables <protocol>_proxy. If no proxy environment variables are set, in a Windows environment, proxy settings are obtained from the registry’s Internet Settings section and in a Mac OS X environment, proxy information is retrieved from the OS X System Configuration Framework.

To disable autodetected proxy pass an empty dictionary.

默认情况下urllib2（测试发现即便没有安装ProxyHandler也是如此）会从http/https_proxy环境遍历中读取代理列表，如果该环境遍历未设置，在Windows环境下将使用IE的代理设置。

测试截图一枚：